Mare and foal walking
Photo courtesy of Outback Reproduction Center.

What To Expect During a Broodmare’s Pregnancy

Much like a woman, every broodmare’s pregnancy is different; however, there are some guidelines for what to expect when she’s expecting.

It’s both an exciting and stressful experience waiting for a broodmare to foal. From the time of conception through foaling, a mare’s body and attitude change. While each mare is an individual, there are signs a broodmare owner or mare manager can watch for to ensure a safe and successful pregnancy.

Nick Kalafatic, DVM, and his wife, Jennifer, handle more than 2,000 broodmares in a season at their state-of-the-art equine reproductive facility, Outback Reproduction Center, in Caldwell, Idaho. For 17 years, their lives have revolved around breeding and foaling. As managers of the largest recipient mare herd in the northwest and a receiving embryo station that specializes in embryo transfer, they offer advice for mare owners eagerly watching their mares for signs a healthy foal is developing.

First, Consider This

The Kalafatics see every kind of mare during a breeding season. From the in-shape performance athlete to the older, arthritic, proven mare that may produce one more foal, each is an individual with different needs. Two points the Kalafatics educate their clients on are mares with chronic lameness and the need for exercise during pregnancy.

Performance mares with a slight lameness that keeps them out of competition can appear to be perfectly sound for breeding. But, that may not always be in the mare’s best interest. Lameness becomes more acute during a pregnancy, Jennifer said. “An older mare that maybe has arthritis that isn’t a big problem when the mare is not heavy in foal may become a problem in the last trimester,” said Nick, a graduate of the University of Missouri at Columbia veterinary program. “A deeply bedded stall is in their favor. Some mares even require a low dose of anti-inflammatory medication during that third trimester if they have a chronic problem with arthritis. “We try to educate people on that point up front. If they have a mare that’s barely getting along before breeding, they need to really [re]consider the decision to breed that mare because the lameness is going to be a lot different when she is heavy in foal.”

Additionally, some of the issues seen during a mare’s pregnancy, such as edema build up, can be dealt with non-medicinally through exercise. “We definitely believe that activity and exercise is in the best interest of the mare,” Jennifer said. “We don’t believe in forced exercise, especially during the last trimester, but it is definitely better for them to be active and moving around.

“It is individually based, because if a performance mare is in shape when they get in foal, you can continue activity clear up until the last trimester of pregnancy. But if it is an activity they are not used to, I wouldn’t start or increase the activity. We encourage activity until the last trimester.” Before breeding a mare, think about how carrying extra weight will affect her quality of life throughout the pregnancy. Once a decision is made and a mare is confirmed in foal, there’s a lot to expect during the 320 days of pregnancy.

Mares in the first trimester of pregnancy turned out on pasture.
Pasture turnout is a low-stress way to get pregnant broodmares moving around. Exercise can help alleviate the edema build up that makes a pregnant mare uncomfortable. QHN File Photo.

The First Trimester

Signs of pregnancy vary depending on the mare’s condition at conception, Nick said. If a mare has a foal at her side, she will already have a larger belly than a first-time broodmare. No matter the mare’s status at the time of conception, the most important considerations are her body condition score and keeping her at an acceptable weight for optimum nutrition. “If a mare is nursing a foal and has just become pregnant again, it adds more stress on them. From a nutritional standpoint, they need to be on a good nutrition program if they are lactating and also if lactating and rebred,” he said.

“The biggest thing I would caution people is to watch the body condition score of the mare, and not just look at the belly. Look at the body condition scoring points – the hips, ribs, neck and shoulder – to get a good idea of where your horse is nutritionally. A lot of horses, you don’t have to increase their intake during the first trimester unless they are nursing a foal, and in that case, they should already be on a high-calorie diet.” Using a body condition score (BCS) of 1 through 9, Nick recommended a mare without a foal at her side be a score of at least 5. For a mare with a foal, shoot for a BCS of 6 at conception.

Outward signs of conception are few in the first trimester. “You won’t see any enlargement in the belly or other noticeable difference except for a lack of heat cycle,” Nick explained. The lack of heat cycle is often attributed to attitude changes in pregnant mares. Though horse dependent, much like a person’s personality is individualized, attitude change is often the first big sign of pregnancy. “Some mares are way kinder when pregnant because they aren’t going through heat cycles, and a smaller number of mares are way grumpier when pregnant,” he said. “That is totally dependent on the mare’s personal behavior. Most mares are more like a gelding when they are pregnant.”

From the first time the broodmare is confirmed in foal, watch for vaginal discharge or early bag development. These are both signs the mare should immediately be seen by a veterinarian, Nick cautioned.

Halfway There

Throughout a mare’s pregnancy, whether she is out to pasture or in a stall, body condition should be continually assessed. In the second trimester, Nick recommended a mare maintain a BCS score in the 6 range in preparation for the third trimester. At the end of the first trimester and beginning of the second, the foal fetus will be roughly the size of a small cat. It is in the midst of the second trimester that the mare will begin to show a “pregnant belly.” “You will start to see some belly size a little bit through filling in the flank,” Nick said. “A grass belly just gets big, but the pregnancy belly is filling in the flank. The belly will get a little bigger, and you want to maintain the same BCS at that time.”

Mare owners should watch for a return of the mare’s heat cycle or any early mammary development. These are causes for concern. “If they start to make a bag or any vaginal discharge of any kind, call a veterinarian immediately,” he advised. “A return to heat cycle is a concern the mare has reabsorbed the baby.” Owners should not be alarmed if the mare develops a larger appetite and becomes a little less active, Jennifer said. “You will notice the mares are less active, because it isn’t as comfortable for them to move around a paddock or a pasture, and they will lay down more,” she explained. “At the end of the second trimester and into the third, one thing a lot of clients notice is that a mare will build edema from the knee and hock down, or in the area in front of their bag. That is a result of lack of activity. If there is edema present, we recommend increased turnout or hand walking – more exercise for those mares.”

At the end of the second trimester, the foal fetus is about two feet long and roughly the size of a medium-sized dog. Moving into the third trimester, a 40-pound fetus should double in size and weight. With this increased growth, the third trimester can be the hardest and result in the most visible changes in a broodmare.

Mare with a "pregnancy belly".
After crossing the halfway point of gestation, the broodmare will get a “pregnancy belly” that fills in at the flank. QHN File Photo.

The Final Stretch

In the third trimester, the foal’s increased size and weight results in an uncomfortable mare. The mare’s outward appearance will show the most changes. That isn’t only a larger belly, but also swelling in her legs and near her bag. Jennifer’s experience has taught her that hearing a mare groan is not always cause for her to be alarmed. “The mares will lay down and groan, and many people mistake that for labor,” Jennifer explained. “A mare can lay down and groan for 20 minutes, then get up and eat like nothing happened. A foal may get a front leg in a bad position of the spine area of the mare, and it almost makes them act colicky. You can treat that with Banamine to help them get over that.”

Healthy mare and foal
A healthy foal is typically born weighing around 100 pounds, a stark difference from a few months earlier, when the fetus was the size of a beagle or lamb. Courtesy of Outback Reproduction Center.

With so much of the mare’s nutritional intake going to the developing foal, a BCS range of 6 to 7 is necessary in the final trimester. Mares will consume more and move less. Exercise and activity can continue to help keep edema from developing, but Jennifer cautioned against forcing a mare to do more than she is willing. Increasing turnout time is one way to get increased activity without undue stress.

There are two major signs of concern to watch for during the final days of pregnancy: milk production outside of the three weeks prior to the projected due date and vaginal discharge. “In the last trimester, some people think it is normal for a mare to have discharge prior to foaling, but it is not normal,” Jennifer warned. “Any white or milky discharge is a sign of placentitis, and that does need treatment. It is important because some people relate it to different animals and think she is ready to foal. She is not.”

Approximately three weeks prior to foaling, a mare will begin to produce milk. Mammary development prior to that is a red flag. “Any milk production that is outside of three weeks prior to the projected due date is not normal,” Nick said. “A mare may get edema near their bag, so a lot of people mistake it for early mammary development. But, any milk production prior to three weeks from the foaling date is a red flag and the sooner you address it, the better chance you have of saving the foal.” As the days count down to 320 and foaling is imminent, knowing a mare’s typical behavior will help alert owners to when she starts to have contractions.

“If you are familiar with your mare, you will absolutely see an attitude change within the last 12 to 24 hours before she foals,” Jennifer said. “An example of that – some mares that are super quiet in a stall situation, when they start having contractions, they will start weaving in the stall. That is an abnormal behavior and they are starting to foal. “Some mares will paw the ground or be super aggressive to the mare next to them,” she continued, noting that on average a healthy foal is born at around 100 pounds. “It is individually based on how the mares act, but there is absolutely a change in behavior before they foal.”

Keeping watch over a pregnant mare can be stressful. Knowing the signs of concern and the typical progression in a healthy pregnancy can make the experience smoother and more enjoyable. It can be a long 320 days, but a healthy foal makes the wait worthwhile.